A wide variety of medical conditions and disorders have been successfully treated using miniature implantable medical devices. For example, one type of implantable medical device is an implantable stimulator. Implantable stimulators stimulate internal tissue, such as nerves, by emitting an electrical stimulation current according to programmed stimulation parameters.
One class of implantable stimulators, also known as BION® devices (where BION® is a registered trademark of Advanced Bionics Corporation, of Valencia, Calif.), are typically characterized by a small, cylindrical housing containing electronic circuitry that produces an electric stimulation current between spaced electrodes. These stimulators, also referred to as microstimulators, are implanted proximate to the target tissue so that the stimulation current produced by the electrodes stimulates the target tissue to reduce symptoms or otherwise provide therapy for a wide variety of conditions and disorders.
For example, urinary urge incontinence may be treated by stimulating the nerve fibers proximal to the pudendal nerves of the pelvic floor. Erectile or other sexual dysfunctions may be treated by providing stimulation of the cavernous nerve(s). Other disorders, e.g., neurological disorders caused by injury or stroke, may be treated by providing stimulation to other appropriate nerve(s).
An example of an implantable device for tissue stimulation is described in U.S. Pat. No. 5,312,439, “Implantable Device Having an Electrolytic Storage Electrode.” U.S. Pat. No. 5,312,439 is incorporated herein by reference in its entirety.
Another exemplary microstimulator is described in U.S. Pat. No. 5,193,539, “Implantable Microstimulator,” which patent is also incorporated herein by reference in its entirety. This patent describes a microstimulator in which power and information for operating the microstimulator are received through a modulated, alternating magnetic field. This is accomplished with a coil in the microstimulator that is adapted to function as the secondary winding of a transformer. This induction coil receives energy from an external device outside the patient's body. A capacitor is then used to store the received electrical energy. This stored energy can then be used to generate a stimulation current through the microstimulator's exposed electrodes under the control of electronic control circuitry.
In U.S. Pat. Nos. 5,193,540 and 5,405,367, which patents are incorporated herein by reference in their respective entireties, a structure and method of manufacture for an implantable microstimulator are disclosed. The microstimulator has a structure which is manufactured to be substantially encapsulated within a hermetically-sealed housing that is inert to body fluids. The microstimulator structure is also of a size and shape capable of implantation in a living body with appropriate surgical tools. Within the microstimulator, an induction coil receives energy or data from outside the patient's body.
In yet another example, U.S. Pat. No. 6,185,452, which patent is likewise incorporated herein by reference in its entirety, discloses a device configured for implantation beneath a patient's skin for the purpose of nerve or muscle stimulation and/or parameter monitoring and/or data communication. Such a device contains a power source for powering the internal electronic circuitry. This power supply is a battery that may be externally charged each day. Similar battery specifications are found in U.S. Pat. No. 6,315,721, which patent is additionally incorporated herein by reference in its entirety.
In another example, such microstimulator systems prevent and/or treat various disorders associated with prolonged inactivity, confinement or immobilization of one or more muscles. Such microstimulators are taught, e.g., in U.S. Pat. Nos. 6,061,596 “Method for Conditioning Pelvis Musculature Using an Implanted Microstimulator;” U.S. Pat. No. 6,051,017 “Implantable Microstimulator and Systems Employing the Same;” U.S. Pat. No. 6,175,764 “Implantable Microstimulator System for Producing Repeatable Patterns of Electrical Stimulation; U.S. Pat. No. 6,181,965 “Implantable Microstimulator System for Prevention of Disorders;” U.S. Pat. No. 6,185,455 “Methods of Reducing the Incidence of Medical Complications Using Implantable Microstimulators;” and U.S. Pat. No. 6,214,032 “System for Implanting a Microstimulator.” These patents are incorporated herein by reference in their respective entireties.
It is often desirable to remove or explant a medical device, such as a stimulator, that has been implanted within a patient. For example, an implanted medical device may be removed when the therapy provided by the device is not longer needed or desired. Additional reasons for removing a medical device from a patient include, but are not limited to, battery depletion, poor or unacceptable performance by the device, and device malfunction.
Likewise, it is often desirable to adjust the position an implanted medical device within the patient. For example, the position of an implanted medical device may be adjusted to optimize device performance, stimulate different tissue, or alleviate pain.
However, the depth and location within the patient often make it difficult to remove or adjust the position of many implanted medical devices. Furthermore, scar tissue often typically forms around, and attaches to, a medical device after it has been implanted. This scar tissue may further complicate the removal or repositioning of an implanted medical device. Thus, significant improvements related to the engagement, manipulation, movement, interconnection, implantation, and explantation of implantable medical devices are desirable.